Pulmonary vascular responses to inhalation anaesthesia in isolated dog lungs

To study the mechanisms of action of four inhalation anaesthetics (diethyl ether, halothane, methoxyflurane, and nitrogen monoxide) upon the pulmonary circulation, the authors carried out 45 experiments in isolated, perfused and ventilated canine lungs. The effects of the anaesthetics were studied at 1) normotonic perfusion, 2) enhanced pulmonary blood flow, 3) microembolism-induced pulmonary hypertension. In the first two-experimental series, no effects of the test anaesthetics on the pulmonary vascular responses became manifest; at microembolism-induced pulmonary hypertension, halothane lowered the pulmonary vascular resistance, whereas diethyl ether stabilized the elevated vascular tone. Methoxyflurane and nitrogen monoxide had no marked effects on the pulmonary vascular responses. On the basis of their experiences and of data published in the literature the authors conclude that there exist regional mechanisms of action of anaesthetics on the lung vessels, activated by the release or action of mediators.